Os ravens wander for their first few years of life, searching for food in the desolate wastes of the high north. Eventually, though, they settle in a large territory with reliable food, and there they begin to build a nest of smooth polished stones, a favorite trinket these creatures seem to hoard regardless of size or value. They don’t guard their nests viciously unless they have eggs or hatchlings of their own, and tend to wander around to other ravens’ territories to search for mates. It takes many years for ravens to pair up and produce eggs, and during the long, tenuous courtship, the pair may spend days carrying and transferring their collection of stones from one raven’s nest to the other, consolidating their hoards and fussing over which location would be more suitable. The ravens mate for life, and so may reject unsuitable consorts late in the courtship process, but once they have settled on their choice, the ravens will combine their territories and often spend time searching for food and sleeping together. The eggs are produced mid-winter, and both parents take turns incubating their progeny in the down-lined nest, often building up a cover of snow to block the wind. The eggs hatch with the coming spring, when food is more plentiful and the climate warmer. Hatchlings leave the nest quickly, as their parents did before them, regardless of where they were born, but many stick around their parents’ territory for a few years before finding one of their own.

Typically larger than their corax and yagaratsu progenitors, os ravens are named so for their lustrous white plumage. Because of their unusual coloring, hybrid os ravens typically leave their birth lands at the end of their first winter, following the snows north to cold Boreus and the Arkene. Their large size and exceptionally downy coat helps them survive the cold climate, and their color, which elsewhere would make them easy targets, acts as the perfect camouflage amongst the snow and ice of the far north. One might expect from their great size that these creatures might hunt to survive, but they have a surprisingly low metabolism and survive only on bones and marrow. They crack open the frozen desiccated carcasses of other northern animals they come across and use their heavy bills to break the bones into smaller pieces which are consumed slowly, one at a time, to prevent the bird from getting chilled. Because they eat so little, os ravens will often carry off especially delicious parts like the leg bones and store them under rocks to eat later. Their affinity for polished stones makes them easy to appease, and magi will often provide a large carved stone to act as their companion's prize piece.